1. Field of Invention
The present invention relates to a method of operating a scanner. More particularly, the present invention relates to a method of operating a double-sided scanner.
2. Description of Related Art
A scanner is a machine that can be regarded as an intermediate between a photocopier and a camera. In the past, a scanner is an expensive piece of equipment that is deployed by a special user such as an artist. With the progress in computer technologies, there is tremendous drop in the price of the scanner so that a scanner has become an essential peripheral device in most personal computers.
According to the price or function, a scanner may be categorized into several types. In general, scanners can be divided into palm top scanners, paper feed scanners, card scanners, negative film scanners and flatbed scanners. A flatbed scanner has a glass platform for holding a document or a pattern thereon. Data is read into the scanner through the movement of a sensor over the document. Since most flatbed scanner is structurally simple, easy to handle and functionally highly expendable, this is the type of scanner that computer users are equipped.
Most scanners use a fluorescence lamp to serve as a light source because fluorescence lamps require little warm-up time. However, the lamp has an unstable period after the scanner is activated. If the lamp is used for scanning during the unstable period, a flickering of the image may occur. One method of removing such flickering is to use a cold cathode ray tube. However, one major disadvantage of using a cold cathode ray tube is that a longer warm-up period is required. Furthermore, for a double-side scanning operation, two sets of cold cathode ray tubes must be employed. Aside from the long warming period, scanning of both sides of a document of an image simultaneously is not recommended because the light from the two sets of cold cathode ray tubes might interfere with each other. Typically, the scanning of the front and back of a document needs to be carried out with a slight shift in position. Thus, if cold cathode ray tubes are used as the light source of a double-side scanner, complicated control circuits are demanded.